This relates generally to electronic devices, and more particularly, to electronic devices with displays.
Electronic devices often include displays. For example, cellular telephones and portable computers often include displays for presenting information to a user.
Liquid crystal displays contain a layer of liquid crystal material. Display pixels in a liquid crystal display contain thin-film transistors and electrodes for applying electric fields to the liquid crystal material. The strength of the electric field in a display pixel controls the polarization state of the liquid crystal material and thereby adjusts the brightness of the display pixel.
Substrate layers such as color filter layers and thin-film transistor layers are used in liquid crystal displays. The thin-film transistor layer contains an array of the thin-film transistors that are used in controlling electric fields in the liquid crystal layer. The color filter layer contains an array of color filter elements such as red, blue, and green elements. The color filter layer provides the display with the ability to display color images.
In an assembled display, the layer of liquid crystal material is sandwiched between the thin-film transistor layer and the color filter layer. Polyimide passivation layers cover the inner surface of the color filter layer and the upper surface of the thin-film transistor layer. An array of column spacers is formed on the inner surface of the color filter layer to maintain a desired gap between the color filter layer and the thin-film transistor layer. Column spacers are typically formed from hard organic materials such as photoresist.
During assembly operations, the layers of a liquid crystal display can be subjected to lateral forces. Even if great care is taken when handling the color filter layer and thin-film transistor layer, there is a possibility that these two layers will shift laterally with respect to each other. Lateral movement between the color filter layer and the thin-film transistor layer can cause damage to the display. For example, the column spacers can scratch the sensitive polyimide passivation layer material on the thin-film transistor layer, leading to undesirable visible artifacts on the display.
It would therefore be desirable to be able to provide electronic device displays with improved column spacer structures for minimizing scratches during lateral movement between display layers.